I got you bro. Short answer is that it's OK to go over the limit. When you stop working (or when your workplace coverage ends), go to covered California and sign up, listing your current income as zero or whatever. The system will kick you into the Medi-Cal application process. Just follow the breadcrumbs from there.
It takes a while. Everything is done by mail. I finished with employer healthcare in August and didn't get on until November, although they say you're covered when you apply. Not sure if jumping the gun is allowed, but I kinda doubt it.
I'd still max those 401Ks, though. Last bite at that particular apple, and all that.